Method and device for encoding and decoding color enhancement layer for video

Abstract

Enhanced dynamic range requires more than 8 bit representation for single color components of pixels. For this purpose, normal color resolution images and high color resolution images are available. Backward compatibility can be achieved by a layered approach using a color enhancement layer, and a conventional image as color base layer. Both have same spatial and temporal resolution. Encoding of the color enhancement layer uses prediction and residual. A methods for optimized color enhancement prediction is disclosed. Color bit depth prediction is done by constructing a polynomial that approximates for all pixels of one color component of a block the color enhancement layer from the color base layer. A predicted version of the high color resolution image and a residual are generated and updated by a residual. The coefficients are compressed and added as metadata to the data stream.

1. A method for decoding a first color layer of a video image, wherein the first color layer comprises pixels of a given color and each of the pixels has a color value of a first depth, comprising the steps of
 decoding a second color layer of the video image, wherein the second color layer comprises pixels of said given color and each of the pixels has a color value of a second depth being less than the first depth; 
 decoding coefficients of a linear transform function; 
 decoding a residual block or image; 
 applying the transform function having said decoded coefficients to the decoded second color layer of the video image, wherein a predicted first color layer of the video image is obtained; and 
 updating the predicted first color layer of the video image with the residual block or image. 
 
     
     
       2. Method according to the  claim 1 , wherein the step of decoding a residual block or image comprises inter-frame decoding. 
     
     
       3. A device for decoding a first color layer of a video image, wherein the first color layer comprises pixels of a given color and each of the pixels has a color value of a first depth, comprising
 means for decoding a second color layer of the video image, wherein the second color layer comprises pixels of said given color and each of the pixels has a color value of a second depth being less than the first depth; 
 means for decoding coefficients of a linear transform function; 
 means for decoding a residual block or image; 
 means for applying the transform function having said decoded coefficients to the decoded second color layer of the video image, wherein a predicted first color layer of the video image is obtained; and 
 means for updating the predicted first color layer of the video image with the residual block or image.